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Print 26 comment(s) - last by albundy2.. on May 30 at 10:43 AM

Grad student may have discovered economically feasable smart concrete

Most people think of driveways and sidewalks when concrete is mentioned. Concrete is also used as a structural building material in many large buildings around the country. The problem with concrete as a building material is that as it develops cracks, the material becomes weaker.

Researchers are currently investigating ways to make smart materials that can heal themselves from cracks and other minor imperfections as a way to prolong the life of the material and increase its strength. A grad student named Michelle Pelletier from the University of Rhode island has made a discovery that may one day lead to smart materials that are cost effective to produce and easy to use.

Pelletier is a master's degree candidate and has developed a method of embedding microencapsulated sodium silicate healing agents directly into concrete. The idea is that the tiny microcapsules, which hold the sodium silicate agent that reacts with calcium hydroxide naturally in concrete, will rupture when cracks form and release the repairing agent.

When the sodium silicate inside the microcapsules reacts with the calcium hydroxide in the concrete a chemical reaction causes a gel-like material to form that can fill cracks and pores in the area of the crack and hardens in about a week.

"Smart materials usually have an environmental trigger that causes the healing to occur," explained Pelletier, who is collaborating on the project with URI Chemical Engineering Professor Arijit Bose. "What's special about our material is that it can have a localized and targeted release of the healing agent only in the areas that really need it."

Tests of the self-healing concrete have shown that when stressed to near breaking the concrete with the microencapsulated sodium silicate is able to regain up to 26% of its original strength. Standard concrete when stressed to similar levels only regains 10% of its strength. Improvements in the

Another potential benefit of the new self-healing concrete being studied is if by immediately filling cracks in the concrete, water can be prevented from reaching the steel reinforcement bars that are used to add strength to concrete. Water getting to the steel reinforcement bars causes the bars to rust leading to reduced strength.



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thoughts...
By inperfectdarkness on 5/25/2010 1:47:56 PM , Rating: 1
1. a week of cure time is longer than most concrete applications will have undisturbed. i would guess that most would be lucky to have a full 72 hours over the course of a weekend.

2. this isn't going to work on high-test concrete applications. i would be very, very surprised to find that these "built in imperfections" to self-heal would be able to provide the strength necessary for, say, an aircraft parking apron.

3. if the cost is even marginally higher than regular concrete; there won't be any adopters. i can think of a handful of other "advancements" which have yet to reach critical mass on the mainstream market--LED light bulbs, pre-wired prefab homes, etc.




RE: thoughts...
By MozeeToby on 5/25/2010 1:54:45 PM , Rating: 2
I don't think anyone is saying that this would replace concrete everywhere and for everything but there are some situations where the extra time and expense might be worth it. In Milwaukee Wisconsin for instance, they have to go around a couple times a year and knock all the loose concrete off the overpasses and bridges (so it doesn't fall and kill someone). Once enough concrete is gone or damaged salt water (from snow melt in the winter) gets to the rebar and rusts it out very quickly.

The end result is unsafe bridges that need to be replaced more often than the engineers would have ever expected. Even if all it does is keep water away from the rebar, you've got a winner right there for some applications (although, why don't they just coat the rebar in plastic?).


RE: thoughts...
By michael67 on 5/26/2010 3:24:15 AM , Rating: 3
quote:
(although, why don't they just coat the rebar in plastic?).

That would take away the hole purpose of the rebar, as it has to be one whit concrete.

Do galvanized rebars are used in places ware the outside environment could reach's the rebars, but at almost $0.5~1 per kg steel, it costing a lot, and a little less strong then whit out

You will also see that they never use real new rebars, but always rusted ones, for two reasons, 1 to remove the carbon skin from the steel, 2 make the surface more rough, for a better bond whit the concrete.


RE: thoughts...
By pattycake0147 on 5/29/2010 7:41:20 PM , Rating: 2
Some re-bar is coated in epoxy. It is very common to see this put in safety conscious applications such as bridges.


RE: thoughts...
By quiksilvr on 5/25/2010 2:02:39 PM , Rating: 5
If marketed correctly, you could even bottle water and sell it to people at insane prices. A dollar for half a LITER! I know it sounds insane, but I guarantee you people will buy it if you put words like "Smart" or "green" or "eco-friendly plastic" on the label.

All kidding aside, this is very easy to market. Imagine selling concrete that doesn't have cracks? Imagine how well hotels can present their building to guests with pristine sidewalks and smooth walls? Imagine the money saved in repairing these cracks? The steel within your buildings won't be at risk to exposure to the environment, which can corrode your precious building.

Believe me, there is a market for it. Just like there is a market for LED lighting and pre-wired prefab homes.


RE: thoughts...
By michael67 on 5/26/2010 3:45:30 AM , Rating: 3
I agree whit you that marketeers are the chum of the earth when it comes to misrepresentation some use of products.

But on the other hand, when applied the right way they can also have real life benefits.

example: LED TV
The edge-light type is just the same as the cold cathode type, gives the same picture (do uses a little less power, but at a mouths higher initial cost)
Back-light type we zone dimming dose improve black lvl's a lot, and have real world benefits.

The technique discuses here, has real world benefits if used for the right implementations, ore (almost) none if use in the wrong place.

Its up to engineers to use it at the right places


RE: thoughts...
By albundy2 on 5/26/2010 6:35:30 AM , Rating: 2
i hate pedants, but your spelling really sucks... sad thing is, you have a brain from what i can decypher from your posts, but when you write like ur txtng it pisses people off and makes it hard to read.


RE: thoughts...
By michael67 on 5/26/2010 7:30:37 AM , Rating: 4
Yeah English is not my main languish and having mild form of dysorthografie dose not help eider
mixing letters (and words) orders when writhing, but its not problem whit reading


RE: thoughts...
By Kurz on 5/26/2010 9:23:38 AM , Rating: 2
Firefox has a built in spell checker.
Its very handy.


RE: thoughts...
By psychobriggsy on 5/26/2010 10:00:41 AM , Rating: 1
WITH, not WHIT.


RE: thoughts...
By michael67 on 5/26/2010 10:22:48 AM , Rating: 4
Good understandably reading is a handicap to!
quote:
mixing letters (and words) orders when writhing , but its not problem whit reading


No spel check helps if its a correct word but the wrong one 0_o


RE: thoughts...
By quiksilvr on 5/26/2010 11:21:43 AM , Rating: 1
Brian: Say TH.
Stewie: TH.
Brian: Now say WIT.
Stewie: WIT.
Brian: WITH.
Stewie: WHIT.
Brian: WITH.
Stewie: WHIT.
Brian: WITH!
Stewie: WHIT!


RE: thoughts...
By albundy2 on 5/30/2010 10:43:30 AM , Rating: 1
my bad, but it's seriously becomming impossible to tell the difference anymore. i know so many people that are completely normal and have no handicaps that are just fucking lazy. they dont even try at all.

then i get to feel like a dick for picking on someone that has a legitimate problem. so i am genuinely sorry for my comment. i am just venting my frustration wit ppl tht talk lik ths. u wnt 2 go 2 teh mal? can b hrd 2 tel wat ur sayn... yaa meen?1111111!1!


RE: thoughts...
By whiskerwill on 5/25/2010 2:05:43 PM , Rating: 4
You're way off base here. I'm not sure what you mean by left "undisturbed", but concrete develops cracks pretty much continuously. It's just normally a slow process. Even the concrete in airport parking decks and runways. They just inspect it regularly and when the cracks get too large, they repair or replace it.

Using this, the "repair" would happen as the crack propagated, saving time and money.


RE: thoughts...
By Smartless on 5/25/2010 2:14:51 PM , Rating: 2
Now now, let's not be too hasty. There have been many other inventions in the "new discovery" category that are far less likely to see application.

1. True that a week is a long time, but this may be great for say something like a storm with a relatively short time-frame of high stress. During that time, concrete depends on its steel to resist the tensile stress which can crack the concrete covering it. If this stuff fills the gap, that's a world of difference.
2. You are correct. High-test or ballistic concrete may not see this, but hey this is the design stage. When admixtures came out, people thought 10,000psi concrete was pretty good. Parking aprons maybe not, but bridges, buildings, sea walls... possible.
3. It doesn't necessarily have to be mainstream. Ballistic concrete and high strength concrete used in some bridges can have pieces of kevlar in it for added tensile strength.

I think usage of this would probably see light of day faster than fuel cell for everyday cars.


RE: thoughts...
By slashbinslashbash on 5/25/2010 2:56:19 PM , Rating: 2
Well, keep in mind this is the first of its kind. It is still under development. There are definite improvements to be made before it is marketed widely.

I see this as an impressive proof-of-concept.


RE: thoughts...
By Chernobyl68 on 5/25/2010 4:03:36 PM , Rating: 2
I was under the impression that Expoxy-coated rebar effectively eliminated rebar corrosion in new construction?
As far as cure time, it depends on the application and time. Concrete cure time isn't always the critical path. Bridge structural concrete is often given a full 30 day cure.


RE: thoughts...
By Bruneauinfo on 5/25/2010 4:51:33 PM , Rating: 3
i disagree with point 2 and 3. concrete is overdesigned to deal with the fact it cracks and tends to fail over time. having this additive that repairs it as it fails could mean longer design life with lower initial strength requirements - a less expensive mix design due to a lower cement requirement.

to the third point, at least two major considerations are taken when designing concrete - the cost of the concrete and the life of the concrete. a mix design may cost more up front, but if it lasts longer due to the fact it heals itself the product has a longer lifespan and longer periods between repairs.

and as for the issues of reinforcing steel and cracks - especially in concrete exposed to the elements - water getting in cracked concrete causes at least two types of deterioration - the water and air getting through the crack causes the steel to rust faster (rusting steel expands so figure out what happens to the crack), and in freezing temperatures in the winter the water freezes and causes freeze thaw deterioration. so even if the self-healing attribute of this additive gave a minimal return on strength, keeping the water out of the cracked concrete would mean longer life for the product.


RE: thoughts...
By guffwd13 on 5/26/2010 2:55:05 PM , Rating: 2
@ inperfectdarkness

1. architectural concrete usually takes 30 days to fully cure

2. concrete naturally has imperfection. this is saying, those imperfections would recapture 26% of its potential perfect composition OR reacquire 26% of lost strength due to damage / weathering. concrete's main strength is in the rebar. in can still maintain a significant portion of its strength until the rebar is exposed. once the steel becomes exposed and starts to rust, the system is compromised. if this material can help prevent steel from becoming exposed by repairing cracks as they start - this would HUGELY benefit the building industry.

3. if you think those things won't gain enough critical mass by the end of this decade - especially considering recently passed and pending legislation, you're an even bigger idiot than the guy who couldn't think of any applications for oled rolling displays.


Continue!
By StevoLincolnite on 5/25/2010 1:45:58 PM , Rating: 5
quote:
Standard concrete when stressed to similar levels only regains 10% of its strength. Improvements in the


Was getting into it... And just like AT&T was cut off. :(




RE: Continue!
By monomer on 5/25/2010 4:24:15 PM , Rating: 5
...That's what she said?


In the...
By geddarkstorm on 5/25/2010 2:15:06 PM , Rating: 4
quote:
Standard concrete when stressed to similar levels only regains 10% of its strength. Improvements in the


What? "In the" what?! I'm on the edge of my seat here, this is so very mysterious.




RE: In the...
By acase on 5/26/2010 11:23:04 AM , Rating: 2
copy/paste FAIL!


So...
By Farfignewton on 5/25/2010 1:34:45 PM , Rating: 1
quote:
Tests of the self-healing concrete have shown that when stressed to near breaking the concrete with the microencapsulated sodium silicate is able to regain up to 26% of its original strength. Standard concrete when stressed to similar levels only regains 10% of its strength.


Instead of repouring now, we can wait until tomorrow?




RE: So...
By surt on 5/25/2010 6:13:14 PM , Rating: 2
Well, assuming your baseline was a standard 10x over-engineering, now you have twice the strength you need, rather than probably just enough.


just a thought..
By IonlyLikeThemApples on 5/25/2010 2:32:39 PM , Rating: 2
This seems nice...
http://tinyurl.com/36kk7uz




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